In the preparation of Organic Light Emitting Devices (OLEDs), metal cathodes must be prepared in a vacuum vapor deposition device.
Current vapor deposition devices cannot detect a distance between a carrier and a shielding plate in a vacuum environment. Interference detection is performed for a carrier in a vacuum chamber with respect to a delivery mechanism through practical delivery of the carrier, in which it is difficult to determine a precise distance and there is a risk of interference, thereby it is difficult to guarantee delivery safety.